Two concentric circles form an annulus of a width of 10 cm. The radius of the smaller circle is 20 cm. Calculate the area of the annulus.

Correct answer:

S =  1570.7963 cm2

Step-by-step explanation:

r2=20 cm m=10 cm r1=r2+m=20+10=30 cm  S1=π r12=3.1416 3022827.4334 cm2 S2=π r22=3.1416 2021256.6371 cm2  S=S1S2=2827.43341256.6371=1570.7963 cm2

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